3TQA

3T QA procedure

The QA procedure contains several steps. Make sure there is no patch activated while doing them.

1) PIQT

2) Spurious test

3) IQT

4) EPI stability

5) Helium level

PIQT

This scan evaluates internal parameters of the scanner, including the stability of the gradient coils. This is done by scanning a phantom from which the specs are known.

Duration: 20 minutes

Preparation:

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• Get the NVC head coil and 200 mm head phantom and phantom holder.
• Check whether the phantom contains air (bubbles). If so, they shouldn't be larger than about a centimes in width.
• Place the base of the coil on the patient table and remove the cushion.
• Position the phantom in the transverse orientation. The 'T' Marker on the phantom should point to the front side of the magnet as indicated by the red circle on Photo 3.Check whether the phantom is inserted correctly; it should be positioned as far back in the coil as possible (i.e. towards the bore) and it shouldn't be able to rotate sideways.
• Place the top part on the coil.
• Position the coil using the light visor; the beam must be on the horizontal line.
• Use Travel to scan plane to position the coil in the magnet center.

How to run:

• On the scan computer: System --> SPT --> Batch Files --> PIQT
• Right-click --> Run batch

Output:

After the PIQT scan finishes, a window pops up, ignore this window and then:

• Image view --> right click on PIQT --> generate reports.
• This generates an HTML-file with values for the tested parameters. If any values are marked in red, it means that the scanner is out-of-spec.
• Save this file into scdropbox --> 3T_QA --> create a new folder with the current date (e.g. '20220803') --> 'currentdate_PIQT.htm'

What if the PIQT indicates problems:

There are a couple of things that you should check before reporting PIQT issues to Philips.

• Check whether the head coil is closed correctly and check whether the cable from the coil into the table is inserted correctly.
• Check whether the phantom is inserted correctly; it should be perfectly in the middle (no room to wiggle).
• Check if there is too much air (bubbles) in the PIQT phantom (larger than 1 cm).

After checking (and fixing) the above points, redo the PIQT scan and report to Philips if there are still signs of scanner issues (red values).

Spurious test

The spurious test evaluates whether the scanner picks up any non-scanner related radio frequency signals from the scanner room (which shouldn't be present).

Duration: 5 minutes

Preparation:

• Disconnect and remove the head coil
• Get the green/yellow wire from the back
• Put the wire lengthwise (i.e. along the direction of the bore) inside the bore, from approximately the end of the bore (it may even stick out a little, like 20 cm) until the beginning of the table. The wire simulates a subject being present in the scanner, which increases the validity/sensitivity of the spurious test by picking up spurious RF signals from outside the bore as an antenna (which wouldn't be picked up without the wire).

How to run:

• Click on the Windows button
• Look for MR-Development
• Click 'Batch Interpreter'
• Select batch
• Select pbsviq_spurious_t30_180hz_qbc.acq
• Press start icon

Output:

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Photo 6

• After the scan is completed, a new subject should have been created (named 'spur T30 180 Hz/px')
• Open the new created subject in review mode by clicking patients --> open for review
• Select scan, proceed
• Click on the grid-like icon ('Switch to Thumbnail view')
• Drag the scans (each beginning with f0=127..) to the right, resulting in a single panel for each of the four scans. Your view should look something like Photo 6.
• Make a print-screen of the images and save this into scdropbox --> 3T_QA --> folder of current date (e.g. '20220803') --> 'currentdate_spurious.png'

What if the spurious test indicates problems:

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Photo 7

Serious problematic spurious RF issues would manifest themselves as very bright bands on the image with almost black backgrounds. The image in the previous step does NOT display this - it's an example of a completely fine test result. Photo 7, on the other hand, IS an example of a problematic spurious test.

IQT

Duration: 15 minutes

Preparation:

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• Get the head coil, phantom holder and phantom.
• Place the phantom holder into the posterior section of the coil. Make sure that the phantom holder feet align with the mating features in the coil.
• Place the phantom on the phantom holder with the arrows of the phantom pointing in the superior direction (towards the magnet). The superior end of the phantom should contact the coil housing at the top of the head region. Failing to position in this way can lead to unpredictable results.
• Attach the anterior section and align the visor light on the raised mark on the housing.
• Connect the coil and use Travel to scan plane to position the coil in the magnet centre.

How to run:

• On the scan-computer: System --> SPT --> Batch Files --> IQT --> SENSE-HEAD-32 --> SENSE-HEAD-32AH
• Right-click --> Run batch

Output:

After the IQT scan finishes, a window pops up, ignore this window and then:

• Image view --> right click scan name (SENSE_HEAD_32H) --> generate reports
• This generates an HTML-file with values for the tested parameters. If any values are marked in red, it means that the scanner is out-of-spec.
• Save this file into scdropbox --> 3T_QA --> folder of current date (e.g. '20220803') --> 'currentdate_IQT.htm'

What if the IQT indicates problems:

Report to Philips.

EPI stability

Measures the SNR over time; over the dynamics (SfNR and SNR)

Duration: 15 minutes, perform 2x

Preparation:

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• Get the head coil, Sphere_A phantom, foam pads and sand bag.
• The air bubble in the phantom needs to be as small as possible.
• Set up the phantom in the head coil, using foam pads to raise it close to the center of the coil. Secure it with foam wedges (Photo 15).
• Do not use the perspex plate for positioning of the phantom, this positioning device will degrade the quality of the shimming.
• Landmark to the centre of the phantom and move the table to the scan plane.
• NOTE: The scan starts after a waiting period to avoid fluid motion artifacts. Do not skip this waiting time. Skipping the waiting time can result in automatic plan scan problems and can have negative influence on the IQ results.

How to run:

• On the scan-computer: System --> SPT --> Select Batch Files --> fMRI --> SH32H
• Right-click --> Run batch
• After 200sec the fluid is stabilised and the test can run
• Perform test 2x and only look at results of the 2nd run.

Output:

The tool calculates statistics.

• Look for 'Relative STD largest ROI'. This should be lower than 0.2%.
• The ghost graph needs to be stable (straight line).
• Normal values for CDAs are available, DDAS not yet. For DDAS the values are lower, so better.
• Make a print-screen of the images and save this into scdropbox --> 3T_QA --> folder of current date (e.g. ‘20220803’) --> ‘currentdate_EPI_stability.png’

What if the EPI stability tool indicates problems:

If the value is out of spec, the field engineer from Philips needs to fix the issue.

Helium level

MRI scanners (very) slowly leak helium, causing the helium level to decline over time. Therefore, it is good to frequently check the helium level.

Duration: 1 minute

Preparation:

Make sure no other scan is running.

How to run:

• Clink on the Windows button
• Look for MR-Development
• Click 'Display Helium Level'
• Click 'Measure Helium level'

Output:

Write down the helium level (%) in the txt. document which can be found in scdropbox --> #T_QA --> helium_measurements_3T --> '2022_helium_measurements_3T.txt'

What if the helium level indicates problems:

Philips gets notified automatically, but if you indicate a problem it might be good to check with them.